Closed hydraulic transmission apparatus with compensating means for unequal motor volumes



June I947. F. BISZANTZ 2 ,3 9

CLOSED HYDRAULIC TRANSMISSION APPARATUS WITH COMP ENSATING MEANS FOR UNEQUAL MOTOR VOLUMES Filed Now-26, 1945 2 Sheets-Sheet 1 INVENTOR FRED BISZANTZ ATTORNEYS June 17, 1947.

v F. BISZANTZ" ,389 CLOSED HYDRAULIC TRANSMISSION APPARATUS WITH COMPENSATING MEANS FOR UNEQUAL MOTOR VOLUMES Filed Nov. 26., 1945 7 FIG: 3. I

2 Sheets-Sheet 2 INVENTOR FRED BISZANTI ATTORNEYS Patented June 17, 1947 RATUS WITH COMPENSATING MEANS FOR UNEQUAL MOTOR VOLUMES Fred Biszantz, Galion, Ohio, assignor to The Galion Metallic Vault Company, Galion, Ohio, a corporation of Ohio Application November 26, 1945,- Serial No. 630,817

9 Claims.

This invention relates to fluid operable apparatus and particularly to fluid operable apparatus including reciprocating motors.

The particular object of the present invention is to eliminate the surge tank usually employed in connection with a, reciprocating motor and pump and to improve the operation of the motor.

Another object is to provide an improved means for supplying makeup fluid to a pump which drives the ram of a reciprocating motor.

Still another object is to provide in connection with a reciprocating ram and a pump therefor, means for supplying makeup fluid to the pump and also for supercharging the pump during the working stroke of the said ram.

A particular object of this invention is to provide, in connection with the hoist mechanism of a dump truck which has a reciprocating lift ram and. a pump, mechanism for supplying makeup fluid to the pump and for supercharging the said pump whereby the raising and lowering of the dump truck body takes place at the maximum rate of speed.

These and other objects and advantages become more apparent upon reference to the following specification taken together with the accompanying drawings in which:

Figure 1 is a fragmentary side elevation of a dump truck having hoisting mechanism according to this invention;

Figure 2 is a plan view of the truck of Figure l with the truck body removed showing the location of the hoisting. mechanism and the pump booster of this invention, and

Figures 3 and 4 are diagrammatic hydraulic circuits illustrating the action of the hoisting mechanism and the pump booster.

General arrangement In the usual type dump truck there is a body which is pivoted on a frame and adapted for being mounted on a truck chassis. The dump bodie are usually tilted from their resting position to their dumping position by means of a hydraulic ram which is supplied with fluid from a pump that is driven from the truck engine. By means of a suitable reversing valve, the body may be selectively raised or lowered.

The ram of the motor which accomplishes the tilting of the dump body is usually a differential ram, having a larger advancing area than a retracting area.

Accordingly, during the advancing movement of the ram there must be supplied more fluid to the advancing area than is withdrawn from the retracting area. This is usually accomplished by 2 means of a surge tank or a reservoir located in. the frame or chassis of the truck. When such a reservoir is supplied, there is ordinarily supplied therewith extra Valves in order to permit the makeup fluid to flow to and from the pump and motor during their operation, and also, usually, the reservoir is vented to the atmosphere so that the liquid can rise and fall freely therein as the ram reciprocates.

According to the present invention there is provided a second differential ram or booster which is arranged with its smaller area connected with the larger area of the motor ram and its larger area connected with the smaller area of the motor ram. Then, the differential ram or booster reciprocates as the motor ram reciprocates and supplies or absorbs the necessary quantity of makeup fluid. During the advancing stroke of the motor ram, the booster is operable to supercharge the pump with a predetermined pressure thereby promoting free flow of fluid to the inlet thereof and insuring that the lifting of the truck dump body will take place at the maximum speed.

Structural arrangement Referring to the drawings there is generally indicated at H) a truck having chassis members l2. Resting on the chassis members I2 is a frame [4 to which is pivoted as at Hi a dump body It of the usual and well known type.

The body I8 is raised from its resting position to its dumping, or Figure 1 position, by means of a linkage generally indicated at 20 which is actuated by the ram 22 of the motor 24. The cylind'er 26 of the motor 24 is pivoted as at 28 to the frame 14' and pivots thereabout as the dump body is lifted and lowered.

Carried in the truck chassis or in the frame M is a fluid. pump" generally indicated at 30 which is driven by the shaft 32 from the engine of the said truck. A reversing valve at 34 directs the discharge from the pump 30 into either a conduit 36' or a conduit 38 depending onthe position of the said valve as determined by the shifting member 40 thereof.

The conduits 36'- andt8 connect with opposite ends of the cylinder 26 of the motor 2 4 and when one thereof is receiving pressure fluid from the pump, the other isreturning exhaust fluid to the pump.

Also carried in the frame 14, as by means of the bracket 42 is the booster of this invention indicated at 44: The opposite ends of the booster M are connected by the conduits 46 and 48 with the opposite ends of the cylinder 26- of the motor 24.

Referring to Figures 3 and 4, the hydraulic connections and the construction of the booster 44 are more particularly shown.

The booster comprises a cylinder 50 within which is reciprocable a piston 52 which may comprise spaced metal plates 54 and the packing 55. The metal plates and the packing are retained together by a nut 58 which threads on the end of a plunger 60 that extends through the left wall of the cylinder 50. bushing in the said left wall and there are packing rings disposed around the said plunger to prevent leakage to and from the interior of the cylinder 50.

Connected with the left wall of the cylinder 50, as by welding, is an internally threaded member 62 which receives the threaded end of a hollow member 64. The members 64 and 62, when threaded together, form a cylinder within which the plunger 6|] is reciprocable.

As will be seen in Figures 3 and 4, cylinder 64 is connected by the conduit 46 with the left end of motor 24 while the cylinder Si] is connected by the conduit 43 with the right end of motor 24. It will also be noted in Figures 3 and 4 that the work ram of the motor 24 comprises a larger advancing area 66 and smaller retracting area 68. Thus, the differential rams of the motor and booster each have their large area connected with the small area of the other.

In operation, the dump body I8 is in its rest position when the ram 22 occupies its Figure 3 position. In order' to lift the dump body, the valve member Hi of the valve 34 is shifted to its Figure 4 position which directs the pump discharge to the area 66 of the plunger 22 and to the working area of the plunger 69 of the booster. Simultaneouslyflhe area 68 of the work ram 22 and the working area of the piston 52 are connected with the suction side of the pump. During the upward movement of the body 18, the pump withdraws fluid from the right end of the motor 24 and supplies fluid to the left end thereof. Inasmuch as the fluid displaced by the retracting area 68 is less than that required to supply the advancing area 66, the piston 52 and plunger 60 of the booster 44 move rightwardly to displace fluid from the cylinder 55) to the suction side of the pump. It will be apparent that the pressure standing on the plunger 60 from the discharge side of the pump will develop a pressure on the fluid within the cylinder 50 so that the suction side of the pump is supercharged to a pressure which will promote the free flow of fluid to the pump, prevent cavitation, and maintain the speed of operation of the plunger 22 substantially constant and at a maximum.

When the dump body It! is completely lifted, the ram 22, piston 52, and plunger 60 occupy their Figure 4 position. During the lowering of the dump body, the action of the booster 44 is reversed and serves to absorb the surplus fluid discharged from the advancing area 66 of the ram 22.

It will be apparent that this invention eliminates the need for the usual type reservoir and, by utilizing a completely closed system, eliminates the necessity of frequent cleaning of the hydraulic fluid, and has the distinct advantage over the ordinary type reservoir in supplying the makeup fluid to the pump at a pressure substantially above atmospheric. It will also be apparent that the particular size of the booster is dependent upon the ratio of its areas and that these may be apportioned to provide the most economical The plunger 6! slides in aing the larger area of each with th smaller area 7 of the other, and a pump connected to transfer and satisfactory dimensions for the device. While the booster has been shown as a unit entirely separate from the main motor 24, it could be constructed to be attached directly to or integral with the cylinder 26 and thus eliminate any necessity for conduits connecting the motor and booster.

It will be understood that this invention is susceptible to modification in order to adopt it to different usages and conditions and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

I claim:

1. In combination, first and second fluid operable differential rams, channel means connectother thereof with said pump inlet, and means of supplying makeup fluid to said pump during the advancing stroke of said ram and for receiving excess fluid therefrom during the retracting stroke of said ram comprising a differential plunger having its larger area connected with the smaller side of said ram and its smaller area connected with the larger side of said ram.

4. In combination, a work ram having a larger advancing area and a smaller retracting area, a pump having its outlet connected with said advancing area and its inlet connected with said retracting area, and means of supercharging said pump comprising means connected to receive fluid from said pump outlet and to dischargea greater volume of fluid to said pump inlet.

5. The combination, in a hoist mechanism for dump trucks and the like, of a reciprocating hoist motor having a differential ram, a pump and valve connected to supply fluid to one side or the other of said ram, and means of supplying makeup fluid to said pump during the advancing stroke of said ram and for receiving excess fluid therefrom during the retracting stroke ofsaid ram comprising a plunger having opposed areas of different size and having the smaller thereof connected with the large area of said ram and the larger thereof connected with the smaller area of said ram.

6. The combination, in a hoist mechanism for dump trucks and the like of a reciprocating differential hoist ram, a pump connected to supply fluid to the larger area of said ram while withdrawing fluid from the smaller area thereof, and means of supercharging said pump comprisin a device connected to receive pressure fluid from said pump and to discharge a greater volume of fluid to said pump.

7. The combination, in a hoisting mechanism for dump trucks and the like of a differential hoisting ram, a second diflerential ram, a fluid pump, and means to connect the discharge side of said pump to the larger area of one of said rams and the smaller area of the other thereof and the inlet side of said pump to the other sides of said rams for driving said work ram in one direction, and to reverse said connections to drive said work ram in the other direction.

8. In combination, first and second fluid operable motors connected to move together and having differential displacements, a reversible source of fluid pressure for selectively supplying one of said motors while exhausting the other thereof, and means of supplying makeup fluid to said source and fo receiving the excess delivery member, a reversible fluid source connected to supply either of said motors while exhaustin the other, and means of supplying makeup fluid to said source comp-rising first and second expansible chambers connected one to expand when the other contracts and having different displacements, and means connecting the chamber having the larger displacement with the motor having the smaller displacement and the chamber having the smaller displacement with the motor having the larger displacement.

FRED BISZANTZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,343,117 Danna June 8, 1920 1,291,918 Kenney Jan. 21, 1919 2,170,029 Liddel Aug. 22, 1939 

